Encapsulation is a well known technique for presenting active materials such as fragrance, flavour, colouring materials etc. Encapsulate systems fall into two main types: those in which the active material is surrounded by a wall or barrier; and those in which the active material is encapsulated in the matrix of a material. Gums, such as alginates, have been used to encapsulate active materials.
Alginates which are anionic gums, are naturally occurring colloids which are normally extracted from brown seaweed (Phaeophycea), which are used mainly in the form of sodium salts. Sodium alginates give very viscous solutions with water and can be cross-linked to form thermally stable gels by interaction with divalent or trivalent metal ions, typically calcium ions. Using this interaction, active materials may be encapsulated or entrapped in an alginate gel matrix. The colloid is principally alginic acid which is made up of three kinds of polymer segments, one segment containing D-mannuronic acid units; a second segment containing L-guluronic acid; and a third segment containing alternating D-mannuronic and L-guluronic acid residues, joined by 1:4 glycosidic linkages. The proportions of the three polymer segments in alginic acid samples give rise to different properties, for example, the alginate from Laminaria hyperborea, with a large percentage of polyguluronate segments, forms rigid, brittle gels which tend to undergo syneresis.
There is a large amount of literature in the area of fragrance encapsulation, not only to provide fragrance stability but also to develop a fragrance delivery system which provides a perceivable sensory effect. To this end, numerous systems have been tested but there are currently no detergent compositions, for example laundry liquids, in the market place which utilise an anionic gum based encapsulation system containing fragrance.
U.S. Pat. No. 4,389,419 (Lim) concerns capsules of oil soluble nutrients such as vitamins which are formed by making an emulsion of sodium alginate with the nutrient and with optional alcohol-insoluble polysaccharide filler or extender such as dextran, sodium carboxy methyl cellulose, methyl cellulose, dextrins and some soluble starches and sodium carboxy cellulose, and adding the emulsion as droplets to an alcoholic solution containing calcium chloride to give solid capsules.
EP 0202819A (Warner Lambert) discloses encapsulates formed by mixing alginate with active ingredient, particularly to produce a dispersion, and cross-linking the alginate by exposure to divalent cations, for example by spraying the dispersion into calcium chloride to produce particles eg up to 10 micron in diameter. The encapsulates may be used particularly in chewing gum, but also in confectionery, foods, pharmaceuticals, toothpaste etc.
WO 92/20771 (Allied Colloids Ltd.) discloses a particulate composition comprising particles having a substantially anhydrous core comprising a matrix polymer containing active ingredient, a layer of hydrophobic oil around the core and a shell of polymer around the oil layer. The active ingredient is disclosed as a detergent enzyme.
EP 0626 445 A2 (Allied Colloids Ltd) discloses a liquid composition comprising a substantially stable dispersion in a liquid phase of particles which have a size below 20 μm and which comprise a detergent enzyme and protective polymeric material which is impermeable to the liquid detergent concentrates but which releases the enzyme when agitated in aqueous wash liquor.
EP 0266 796 B1 (Showa Denko Kabushiki Kaisha) discloses a water-soluble microcapsules, containing enzymes, which are stably retained in a concentrated aqueous solution containing an agent such as a surfactant and are readily dissolved in water or a dilute aqueous solution. The water-soluble microcapsules utilise a coating material, specifically polyvinyl alcohol with an average degree of polymerisation in the range of 200 to 3,000 and a saponification ratio of not less then 90%. The core material is disclosed as a water-containing polyhydroxy compound.
U.S. Pat. No. 5,281,355 (Lever Brothers company) discloses a heavy duty liquid composition comprising (1) a capsule comprising a component or components normally subject to degradation by components of these compositions; and (2) a composite polymer forming a network in which the component(s) are entrapped and from which network the component(s) are released upon dilution of the concentrated liquids. The composite emulsion copolymer in turn comprises a hydrophilic portion i.e., hydrophilic polymer attached to a hydrophobic particles and a hydrophobic polymer core portion wherein the hydrophilic portion comprises hydrophilic water soluble polymer or polymers physically or chemically attached to said hydrophobic polymer particles.
GB-A-1 390 503 (Unilever Limited) relates to a liquid aqueous detergent composition cantaining capsules which are insoluble in the composition, but which release their contents when the composition is diluted with water, due to the change in ionic strength of the liquid environment of the capsules. The patent discloses capsules containing core material and having at their surface water-soluble polymer gel, in which the electrolyte and its concentration in the medium, and the polymer gel are such that the polymer gel is insoluble in the medium, but dissolves with release of the core material when the composition is diluted with water, preferably the polymer gel forms a wall surrounding the core material.
U.S. Pat. No. 5,716,920 and WO 98/11870 (The Procter & Gamble Company) both disclose liquid personal cleansing compositions including a lipophilic skin moisturising agent encapsulated with a complex coacervate of a polycation and a polyanion. The polyanion may be, eg, sodium alginate. The encapsulate must be substantially free of cross-linking agent for the complex coacervate to have appropriate hardness characteristics.
Our copending PCT patent application number GB98/03345 (WO 99/24159) is directed at alginate encapsulates, and in particular the use thereof in toothpaste.
The present invention provides a detergent composition which utilises an anionic gum based encapsulate containing active material, which dissolves on dilution resulting in release of the active material.